//from http://blog.csdn.net/zouxinfox/article/details/3560891
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>
#include <assert.h>
/*
*线程池里所有运行和等待的任务都是一个CThread_worker
*由于所有任务都在链表里，所以是一个链表结构
*/
typedef struct worker
{
    /*回调函数，任务运行时会调用此函数，注意也可声明成其它形式*/
    void *(*process)(void *arg);
    void *arg;/*回调函数的参数*/
    struct worker *next;
} CThread_worker;

/*线程池结构*/
typedef struct
{
    pthread_mutex_t queue_lock;
    pthread_cond_t queue_ready;
    /*链表结构，线程池中所有等待任务*/
    CThread_worker *queue_head;
    /*是否销毁线程池*/
    int shutdown;
    pthread_t *threadid;
    /*线程池中允许的活动线程数目*/
    int max_thread_num;
    /*当前等待队列的任务数目*/
    int cur_queue_size;
} CThread_pool;

int pool_add_worker(void *(*process)(void *arg), void *arg);
void *thread_routine(void *arg);

static CThread_pool *pool = NULL;
void pool_init(int max_thread_num)
{
    pool =(CThread_pool *) malloc(sizeof(CThread_pool));
    pthread_mutex_init(&(pool->queue_lock), NULL);
    pthread_cond_init(&(pool->queue_ready), NULL);
    pool->queue_head = NULL;
    pool->max_thread_num = max_thread_num;
    pool->cur_queue_size = 0;
    pool->shutdown = 0;
    pool->threadid =
       (pthread_t *) malloc(max_thread_num * sizeof(pthread_t));
    int i = 0;
    for(i = 0; i < max_thread_num; i++)
    { 
        pthread_create(&(pool->threadid[i]), NULL, thread_routine,
                NULL);
    }
}

/*向线程池中加入任务*/
int pool_add_worker(void *(*process)(void *arg), void *arg)
{
    /*构造一个新任务*/
    CThread_worker *newworker =
       (CThread_worker *) malloc(sizeof(CThread_worker));
    newworker->process = process;
    newworker->arg = arg;
    newworker->next = NULL;/*别忘置空*/
    pthread_mutex_lock(&(pool->queue_lock));
    /*将任务加入到等待队列中*/
    CThread_worker *member = pool->queue_head;
    if(member != NULL)
    {
        while(member->next != NULL)
            member = member->next;
        member->next = newworker;
    }
    else
    {
        pool->queue_head = newworker;
    }
    assert(pool->queue_head != NULL);
    pool->cur_queue_size++;
    pthread_mutex_unlock(&(pool->queue_lock));
    /*好了，等待队列中有任务了，唤醒一个等待线程；
    注意如果所有线程都在忙碌，这句没有任何作用*/
    pthread_cond_signal(&(pool->queue_ready));
    return 0;
}

/*销毁线程池，等待队列中的任务不会再被执行，但是正在运行的线程会一直
把任务运行完后再退出*/
int pool_destroy()
{
    if(pool->shutdown)
        return -1;/*防止两次调用*/
    pool->shutdown = 1;
    /*唤醒所有等待线程，线程池要销毁了*/
    pthread_cond_broadcast(&(pool->queue_ready));
    /*阻塞等待线程退出，否则就成僵尸了*/
    int i;
    for(i = 0; i < pool->max_thread_num; i++)
        pthread_join(pool->threadid[i], NULL);
    free(pool->threadid);
    /*销毁等待队列*/
    CThread_worker *head = NULL;
    while(pool->queue_head != NULL)
    {
        head = pool->queue_head;
        pool->queue_head = pool->queue_head->next;
        free(head);
    }
    /*条件变量和互斥量也别忘了销毁*/
    pthread_mutex_destroy(&(pool->queue_lock));
    pthread_cond_destroy(&(pool->queue_ready));
    
    free(pool);
    /*销毁后指针置空是个好习惯*/
    pool=NULL;
    return 0;
}

void *thread_routine(void *arg)
{
    printf("starting thread 0x%x/n", pthread_self());
    while(1)
    {
        pthread_mutex_lock(&(pool->queue_lock));
        /*如果等待队列为0并且不销毁线程池，则处于阻塞状态; 注意
        pthread_cond_wait是一个原子操作，等待前会解锁，唤醒后会加锁*/
        while(pool->cur_queue_size == 0 && !pool->shutdown)
        {
            printf("thread 0x%x is waiting/n", pthread_self());
            pthread_cond_wait(&(pool->queue_ready), &(pool->queue_lock));
        }
        /*线程池要销毁了*/
        if(pool->shutdown)
        {
            /*遇到break,continue,return等跳转语句，千万不要忘记先解锁*/
            pthread_mutex_unlock(&(pool->queue_lock));
            printf("thread 0x%x will exit/n", pthread_self());
            pthread_exit(NULL);
        }
        printf("thread 0x%x is starting to work/n", pthread_self());
        /*assert是调试的好帮手*/
        assert(pool->cur_queue_size != 0);
        assert(pool->queue_head != NULL);
        
        /*等待队列长度减去1，并取出链表中的头元素*/
        pool->cur_queue_size--;
        CThread_worker *worker = pool->queue_head;
        pool->queue_head = worker->next;
        pthread_mutex_unlock(&(pool->queue_lock));
        /*调用回调函数，执行任务*/
       (*(worker->process))(worker->arg);
        free(worker);
        worker = NULL;
    }
    /*这一句应该是不可达的*/
    pthread_exit(NULL);
}
void *myprocess(void *arg)
{
    printf("threadid is 0x%x, working on task %d/n", pthread_self(),*(int *) arg);
    sleep(1);/*休息一秒，延长任务的执行时间*/
    return NULL;
}
int main(int argc, char **argv)
{
    pool_init(3);/*线程池中最多三个活动线程*/
    
    /*连续向池中投入10个任务*/
    int *workingnum =(int *)malloc(sizeof(int) * 10);
    int i;
    for(i = 0; i < 10; i++)
    {
        workingnum[i] = i;
        pool_add_worker(myprocess, &workingnum[i]);
    }
    /*等待所有任务完成*/
    sleep(5);
    /*销毁线程池*/
    pool_destroy();
    free(workingnum);
    return 0;
}